HI Roy
On (02 Nov 96) Roy J. Tellason wrote to Alec Cameron...
 RJ> Alec Cameron wrote in a message to BILL BAUER:
 AC> That works on some faulty nicads of the common sizes [AAA thru 
 AC> D, and camera/ phone/ cordless tool types] but the pulse needs 
 AC> to be less than 12v per cell, and really momentary. 
 RJ> I've never heard of that voltage restriction before,  and have 
encountered
 RJ> various messages where people were saying that they were using somewhat
 RJ> higher voltages,  30-40v being a common figure.
"My" restriction assumes that the donor source is a battery or charger, with
no added series resistor. The pulse is almost a "short" on the donor supply.
 RJ> The usual method seems to be to charge a capacitor and then discharge it
 RJ> rapidly through the faulty cell.
Fine. 30, 40 even more volts on a charged capacitor would be OK. But if the
nicad was a very large one then a very large capacitor would be required. A
capacitor can deliver a large power but with very little energy. "My" method
delivers both high power and high energy.
The worst case for capacitor fed surge, would be the nicad design which is of
spiral construction. If the fault was at the remote end ie away from the
terminals, then the self inductance of that spiral would attenuate the pulse
so by the time it reached the fault, the pulse might fail to zap the fault
clear.   Cheers............ALEC
... ........BUNDANOON, on a dirt track leading to the Info Superhighway
--- PPoint 1.92
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